There has been a long and continuing search for the optimum sleeping mattress. The search has taken many forms but, generally, it can be said that a principal comfort factor contributing to a coil spring type is the support which the coil spring unit used in the mattress may give to the user. If the support is comfortable and maintains the body in a condition which applies no unusual force, it will enhance the rest required by the user.
Elasticity of the bed coil spring unit is important. This is so since with greater elasticity, more constant support over the area of the body of the user being supported is obtained. To obtain such elasticity, rigid elements comprising the bed coil spring unit should be minimized.
Yet a further comfort factor is the symmetry of the bed coil spring unit. The prior art discloses various configurations of bed coil spring units. A typical one of such configurations is illustrated and disclosed in U.S. Pat. No. 4,960,267 entitled EDGE-REINFORCED SPRING BEDDING PRODUCT (Scott). Scott teaches a plurality of helicoils which extend transversely to the body of the user and which are separated a predetermined distance. The helicoils are used to connect adjacent cell units which together comprise the bed coil spring unit. So-called "long legs" extend transverse to the helicoils and define the opposite legs of the individual cell. A pair of coil springs are positioned within the cell with the circumference of each of the coil springs contacting and joined with the helicoils.
A problem with the bed coil spring unit according to the aforementioned Scott reference is that there is no symmetry in the bed coil spring unit within the individual cells. The coil springs are each located closer to one long leg thereby creating an upwardly directed force which acts on one side of the center axis and tends to create a moment acting outside the cell and on the body of a user. This moment has a tendency to move the user toward the side of the bed coil spring unit opposed from the side on which the coil springs are located which is not a comfort contributing factor.